In a wireless power supply system in which a power-feeding coil installed on a ground side feeds power to a power-receiving coil installed on a vehicle without contact, there occurs a problem that a voltage is generated between the vehicle and the ground by a stray capacitance existing between the power-feeding coil and the power-receiving coil. As a conventional example of this type, for example, a technique disclosed in Patent Literature 1 is known. Patent Literature 1 discloses a technique for preventing a radiated electromagnetic field from being generated around a wireless power supply device.